Die-press forming systems are used in the manufacture of a variety of shaped products. For example, a forming press system for making pressware containers from paperboard typically includes one or more forming die assemblies oriented on an inclined plane such that scored paperboard blanks are fed between upper and lower die components thereof by way of gravity. Generally, forming die assemblies include an upper male die member or “punch,” and a lower female die member or “die,” which are compressed together to shape and crimp the blank into the desired final product.
The female and/or male die members of a forming die assembly are commonly provided with one or more product ejectors or “knock-out” members for assisting in the removal of the formed product. For example, U.S. Pat. No. 7,070,729 to Johns et al., U.S. Pat. No. 6,783,720 to Johns et al., U.S. Pat. No. 4,755,128 to Alexander et al., and U.S. Pat. No. 1,793,089 to Heyes, are all incorporated herein for background information. These knockout members may serve a number of purposes in the manufacturing process. As a paperboard blank is fed into a die assembly, the bottom knockout may be raised to support and guide the blank into position over the lower die. As the die assembly is closed, the bottom knockout also commonly provides a clamping surface to hold the blank against the upper punch and maintain the blank on-center as it is pressed into the die and shaped into the desired product configuration. And when the die assembly is opened, the bottom knockout releases and ejects the formed product from the lower die.
Typically, the bottom knockout member of a forming die assembly is machined in the general shape of the product being produced (e.g., round, oval, rectangular, etc.), and having dimensions closely matching the bottom of the finished product surface area. For example, in a circular die assembly for forming circular pressware plates or bowls, the bottom knockout member is typically a circular disk having a diameter matching the full outer diameter of the bottom panel of the plate or bowl to be formed, and is mounted concentrically within the circular lower die. The bottom knockout member will typically be fabricated from the same material as the other die components, commonly ductile iron. As a result, known bottom knockout components tend to have substantial weight.
The considerable weight of known bottom knockout components, coupled with the high-speed cyclical nature of their operation, has been found to contribute significantly to wear and fatigue-related damage to supporting equipment. And because forming die assemblies are commonly oriented at an inclined angle to facilitate loading and discharge, friction wear of bushings supporting the bottom knockout components is accelerated, particularly on the “downhill” side of the bearing surfaces. Equipment misalignment resulting from wear of component surfaces may negatively affect product quality. Moreover, maintenance costs for replacement of worn components, as well as lost productivity due to equipment down-time during repairs, can significantly decrease production volume and profitability.
Accordingly, if can be seen that improvements to reduce the incidence of wear and other damage to components of forming press or die equipment are highly desirable in terms of improved product quality, greater productivity and increased profitability.